The disclosures herein relate generally to apparatus for cooling heat generating devices. More particularly, the disclosures herein relate to apparatus for cooling heat generating devices in computers.
Some processor configurations utilize a pin and socket type mounting technique for mounting the processor on a printed circuit substrate. This type of mounting technique tends to use a lot of space on the printed circuit substrate. Space constraints combined with signal bus routing requirements dictate certain processor configurations in a 4-processor computer such as a server. The space constraints are particularly stringent in a multiple-processor computer having a small form factor.
Several conventional configurations meet the space and signal routing requirements. However, in these conventional configurations at least two of the processors and associated heat sinks are in-line with each other with respect to an air flow axis of an adjacent cooling fan. Furthermore, in conventional in-line configurations, the heat sinks associated with each processor are at approximately the same elevation with respect to a mounting surface of the printed circuit substrate.
U.S. Pat. No. 5,912,802 discloses a device and a method for cooling an integrated circuit package, such as a microprocessor, within an enclosure of a computer. The device includes a blower, a first heat sink attached to the microprocessor, and a first air duct coupling the blower to the first heat sink. The blower has an air intake for inducting ambient air from outside of the enclosure. The blower generates an air stream which flows through the first air duct to the first heat sink for cooling the microprocessor. A second air duct connected to the first heat sink may be used to subsequently direct the air stream to a second heat sink for cooling a second microprocessor. However, the cooling of the first microprocessor increases the temperature of the air stream, reducing the effective heat transfer at the second microprocessor.
U.S. Pat. No. 5,828,549 discloses a method and an apparatus for dissipating heat from an electrical device and for routing air from one place to another. In a computer having several heat generating devices, a heat sink is thermally attached to each one of the devices. Each of the heat sinks has a base, two side walls and a top wall forming a passage therebetween. The base, side and top walls are all thermally conductive to the corresponding heat producing device, and therefore each of them radiate heat into the passage. Each of the heat sinks also includes several cooling fins that extend into the passage, thereby increasing the thermal efficiency of the heat sink. Furthermore, the passage is of sufficient size to allow multiple heat sinks to be serially in-line, thereby allowing an air mass to flow from one heat sink to another.
In a conventional in-line configuration, an upstream heat sink is subjected to a cooler air stream than a downstream heat sink. The heat dissipated from the upstream heat sink substantially heats the air stream. The heating of the air stream by the upstream processor dramatically reduces the amount of heat transfer from the downstream heat sink to the air stream. The reduction in heat transfer at the downstream heat sink can result in the downstream processor becoming overheated.
The heat transfer efficiency of the downstream heat sink in conventional in-line configurations can be improved using a forced air device, such as a very large fan or a blower, capable of delivering air flow at high pressures and volumes. These forced air devices are large, taking up a significant amount of space. Because of the inherent air flow limitations and heating of the air associated with heat sinks in conventional in-line configurations, the use of a large cooling fan to compensate for poor cooling efficiency provides negligible cooling reserves.
Another conventional technique for enhancing the cooling efficiency of the downstream heat sink in a conventional in-line processor configuration includes using an air duct to direct some of the cool air directed from the fan to the downstream heat sink. The air duct typically also includes a portion for directing the exhaust air from the upstream heat sink away from the inlet to the downstream heat sink. This technique requires the upstream and downstream heat sinks to have a considerable amount of physical separation in order to provide room for the air duct. This physical separation takes up additional space in an already constrained area.
Accordingly, what is needed is an apparatus that economically and efficiently transfers heat from a plurality of in-line heat sinks and that occupies a reduced amount of space.
One embodiment, accordingly, provides a cooling apparatus that positions in-line heat dissipating bodies at different elevations with respect to a reference surface to enhance the transfer of heat from each one of the heat dissipating bodies to a stream of air. To this end, an apparatus for cooling a plurality of heat generating devices includes a support member and a plurality of heat dissipating devices attached to the support member. A first one of the heat dissipating devices includes a first heat dissipating body positioned at a first elevation above a mounting surface of the support member. A second one of the heat dissipating devices includes a second heat dissipating body positioned at a second elevation above the mounting surface of the support member.
A principal advantage of this embodiment is that each heat dissipating body is subjected to a substantially unheated stream of air, improving cooling efficiency.